This invention relates in general to material crushing and comminuting equipment, and in particular relates to equipment for crushing and comminuting materials such as mineral ores from a quarry or mine.
Various types of crushing and pulverizing equipment have heretofore been used for comminuting minerals ores and other similar hard, rock-like material. Raw material from a quarry or mine is typically reduced in a multi-stage operation which includes a primary stage for coarse reduction, one or more secondary stages for intermediate size reduction, and a third or pulverizing stage for fine size reduction. In the primary stage conventional equipment which has been employed includes jaw crushers, gyratory crushers and cone crushers. Secondary stage crushing equipment conventionally includes hammer mills, jaw, gyratory or cone crushers, and roll type crushers. The pulverizing stage equipment commonly includes ball and tube mills, rod mills, hammer mills and roller pulverizers and the like.
Conventional ball and tube mills and rod mills employ rotating shells containing a plurality of tumbling steel balls or rods which reduce the contained material by impact and attrition. In conventional mills of this type the start-up power requirements are substantially larger than the running power requirements, thus necessitating a drive motor of relatively large horsepower rating to achieve start-up. In such mills it is also necessary to start and stop the mill following set procedures so that there is a minimum load of product material when either starting or stopping. In addition, wear of the elements on mills of this type is a problem with the result that relatively frequent maintenance and downtime is required. Furthermore, over-grinding and ore sliming are problems encountered with conventional pulverizing stage equipment.